I'd say pick and choose based on how your shammy is played. +8% or +10% to the specific spells you use is pretty nice.
For my healer focused sham, after the Arch/Class AA tab healing stuff, I bought the Improved/Focuses for healing stuff then the Synergy (+10k to next 3 heals for all party members every time you Cloud.) Then the few dots/nukes I kept on spell bar and rest was dump AA for max time.